Dirichlet is not just bad and singular in many rational IFS fractals


SCHLEISCHITZ J.

Quarterly Journal of Mathematics, vol.75, no.1, pp.11-29, 2024 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 75 Issue: 1
  • Publication Date: 2024
  • Doi Number: 10.1093/qmath/haad039
  • Journal Name: Quarterly Journal of Mathematics
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Academic Search Premier, Applied Science & Technology Source, MathSciNet, zbMATH, DIALNET
  • Page Numbers: pp.11-29
  • Middle East Technical University Affiliated: Yes

Abstract

For m ≥ 2, consider K the m-fold Cartesian product of the limit set of an iterated function system (IFS) of two affine maps with rational coefficients. If the contraction rates of the IFS are reciprocals of integers, and K does not degenerate to singleton, we construct vectors in K that lie within the 'folklore set' as defined by Beresnevich et al., meaning that they are Dirichlet improvable but not singular or badly approximable (in fact our examples are Liouville vectors). We further address the topic of lower bounds for the Hausdorff and packing dimension of these folklore sets within K; however, we do not compute bounds explicitly. Our class of fractals extends (Cartesian products of) classical missing digit fractals, for which analogous results had recently been obtained.